Solid polyelectrolyte polymer film

ABSTRACT

This invention relates to a solid polyelectrolyte polymer film which comprises a polymer, a plasticizer for the polymer, an epoxidized vegetable oil, and an electrolyte.

BACKGROUND OF THE INVENTION

This invention relates to a solid polyelectrolyte polymer film comprisedof a single polymer sheet or film which contains electrochemical speciesand which can be used as a static dissipative film, or be connected tocurrent collectors on each of its two sides, forming a secondarybattery.

Most simple salts are not good electrical conductors. However, a varietyof solids have high ionic conductivities which range from hard,refractory materials, such as sodium beta-alumina, through softermaterials, such as silver iodide (AgI), to the very soft polymerelectrolytes. Stoichiometric (AgI), nonstoichiometric (sodiumβ-alumina), or doped compounds (calcia-stabilized zirconia) are includedin the list. Most electrically conductive metals have values above 10⁵ ;whereas, insulating materials have typical values lower than 10⁻¹⁶(ohm-cm)⁻¹.

At temperatures above 150 degrees C., silver iodide shows increasedelectrical conductivity which results from movement of silver cations.This can be shown by placing silver electrodes on either side of asilver iodide pellet. After the desired amount of time, the silverplates were reweighed. The negative plate gained silver while thepositive plate lost silver, and that difference was the same as expectedif silver cations carried the charge. It has been reported that evenionic solids such as sodium chloride have some electrical conductivitythat are not electronic but ionic.

A model of how crystal lattice defects can promote ionic motion(diffusion) over long molecular distances has been proposed by Shriveret al., Solid State Electronics, 5, '83 (1982). If ionic solids hadperfect ordered structure, every lattice site would be occupied by theappropriate ion. However, every structure is not perfect. Defects arisewhen ions exist in interstitial sites or when vacancies exist in siteswhich are normally filled. Frenkel disorder is defined as the hopping ofions through a series of interstitial sites, and Schottky disorder isdefined as the hopping of vacancies through normal lattice positions.These disorders produce ionic conductivity in solids.

Many studies have shown that most crystalline inorganic electrolytesexhibit this behavior. All have a low-conductivity phase in which theions are ordered. They exist in subsets of lattice sites. At highertemperatures these ions become disordered and ionic conductivity isincreased. High conductivity depends on how fast ionic migration(transport) occurs. If the energy needed to disrupt ions in theavailable sites and needed to transport ions to vacant sites in thedisordered phase is low, high ionic conductivities will result.

Compounds which contain a subset of ions which are located among a largegroup of vacant sites can undergo fast ionic transport if there isenough energy to disorder the ions among the available sites and if theenergy is great enough to move ions from filled to vacant sites. Ifthese energies are low, then, the conductivity can be high. Such acompound is betaalumina. For example, the sodium/sulfur battery operatesutilizing this principle at 300 degrees C. A sodium beta-alumina ceramictube is used to separate the molten sodium positive electrode from themolten sulfur negative electrode. Sodium is oxidized during discharge atthe sodium/sodium beta-alumina interface. The resultant sodium cation istransported through the beta-alumina (solid electrolyte) where iteventually combines with reduced sulfur in the outer chamber to formsodium polysulfide. The sulfur electrode contains enough carbon to makeit electronically conducting. During the charging mode, this process ifreversed.

In all electrochemical cells, whether they are batteries or sensors, theelectrolyte is essential since the principle electrochemistry occurs atthe interface between the electrodes and the electrolyte. At theinterface, a metal atom (electrode) can be oxidized to a metal cationwhich can enter the electrolyte while metal cations from the electrolytecan be incorporated into the other electrode such as titanium disulfide.Therefore, the electrolyte's role is to provide a path for the migrationor diffusion of ions from one electrode to the other. This flow ofcharge can be offset or balanced by the flow of electrons through anexternal circuit. For example, a battery or a sensor requires that theelectrolyte cannot conduct electrons or be electronic conductive. If itdoes conduct electrons, the battery would discharge (short-out) as itstands. In other words, the electrolyte must be a good ionic conductorand a very poor electronic conductor.

The primary reason why solid-state batteries have not been verysuccessful is the dimensional changes which take place in the electrodesduring charging and discharging. For example, a lithium negativeelectrode oxidizes as the battery discharges which slowly strips lithiummetal away from the metal-electrolyte interface. If the interface cannotdeform to maintain good interfacial contact, the battery will fail.Also, the insertion of lithium cations into the titanium disulfidepositive electrode can swell the electrode which also diminishesinterfacial contact. Instead of using hard, crystalline solidelectrolytes which loose interfacial contact during discharge, soft,flexible polymeric electrolytes could deform or flow and continuallymaintain interfacial contact with the electrodes. Polymeric electrolytescan also be cast as thin films which can lower the resistance of theelectrolyte, its volume and weight.

In an attempt to solve this problem and reduce the dimensions ofsecondary batteries, recent battery research has turned to the use ofpolymeric films in secondary batteries. See European patent applicationNo. 84107618.5 June 30, 1984. The use of polymeric films can providebatteries having very thin crosssections and decreased weight.

In a further improvement, Noding et al. U.S. Pat. No. 4,714,665,teaching a three-layer polymeric film secondary battery, and U.S. Pat.No. 4,728,588, teaching a single polymer film layer in a secondarybattery, provide additional diminution of the dimensions of the filmlayers. It has now been recognized that the polymeric film containingthe electrolyte species used in the inventions of the foregoing patentsis a separate and heretofore unclaimed invention.

It is therefore an object of this invention to provide a novel solidpolyelectrolyte polymer film, which is useful in a secondary batterywhich incorporates the utilization of a single polymeric film and which,as a result, has a very thin cross-section even when constructed of aplurality of cells.

THE INVENTION

This invention provides a solid polyelectrolyte polymer film comprisedof: a polymer; a plasticizer for the polymer; an epoxidized vegetableoil; and electrolyte disassociatingly solubilized in the plasticizer,such as a conventional electrolyte or a salt having the formula MXhd awherein X is chloride, bromide or iodide; M is a metal ion having areduction-oxidation potential greater than that of X; and a is theoxidation number of M.

The electrolyte can be any conventional electrolyte which is soluble inthe plasticizer constituent of the polymer and which does notdeleteriously affect the polymer film properties or the plasticizingfunction of the plasticizer. Especially suitable electrolytes are alkalimetal tetraphenylborates and thiocyanates. Most preferred of these aresodium tetraphenylborate and lithium and sodium thiocyanate. Since theseelectrolytes are salts, their concentrations in the polymer film shouldnot be so high that the polymer film is rendered electronicallyconductive. For example, it has been found that, when sodiumtetraphenylborate is the electrolyte, di(triethylene glycol butylether)terephthalate is the plasticizer, poly(vinyl chloride) is the polymer,and the film thickness is within the range of from about 2 to about 20mils, the sodium tetraphenylborate is preferably present in an amount ofabout 1 weight percent based upon the total weight of the polymer film.Sodium tetraphenylborate amounts above about 7 weight percent generallyrender the polymer film so electronically conductive that, for example,a short will occur between the electronically conductive polymer filmsof a secondary battery made from such film, thus rendering it of littleuse.

The MX_(a) salt is preferably Zn, an alkali metal or an alkaline earthmetal salt. Preferred of these are Li, Ca, Na, Zn and Mg. The halideconstituent is preferably iodide as the use of chloride, bromide orfluoride results in a loss of these halides from the film because oftheir gaseous evolution therefrom. The selection of the M and X coupleis, in all cases, such that the reduction-oxidation potential of M isgreater than that for X. The difference in potential is preferablygreater than 0.5 volts, as a smaller difference does not provide avoltage which would be useful to adequately power most present daydevices. Salts exhibiting relatively high voltage output for thesecondary battery of this invention are CaI₂ and LiI.

It is desirable to maximize the amount of electrolyte salt which can beuniformly distributed within the polymer film. The maximization of thesalt concentration is dependent upon the solubility of the salt in theplasticizer and upon the amount of plasticizer which can be used withthe polymer without deleteriously affecting the latter's properties. Toinsure good solubility, the M constituent of the MX_(a) salt should havea Pauling's electronegativity less than that for X by at least 0.1units. Salt concentrations in the plasticizer within the range of fromabout 5% to about 30% of total salt saturation are deemed adequate toexcellent for the purposes of this invention.

Besides the plasticizer being a good salt solvent, it has to alsomaintain its plasticizing function and be highly compatible with andable to maintain a continuous phase throughout the polymer. There arenumerous plasticizers which may be used. Suitable plasticizers areexemplified by alkylene glycol alkanoic diesters and by alkyletheresters of benzoic acid; terephthalic acid; phthalic acid; and adipicacid. Preferred alkylene glycol alkanoic diesters have the formula:##STR1## wherein X is a whole integer greater than or equal to 2 butless than or equal to 5, n is a whole integer greater than or equal to 4but less than or equal to 12, and m=2n+1. Of this class of diesters, thecompounds 2-ethylhexanoic tetraethylene glycol, 2-ethylheptanoictetraethylene glycol, 2-ethylhaxanoic triethylene glycol,2-ethylheptanoic triethylene glycol, and mixtures thereof are especiallypreferred. These diesters are commercially available from C. P. Hall,Inc., of Chicago, Ill., and are marketed under the name of TEGMER. Theseplasticizers are suitably present in the polymer film in an amount offrom about 30 to about 60 weight percent based upon the total weight ofthe polymer film.

A preferred plasticizer is an ether ester of terephthalic or adipic acidhaving the formula: ##STR2## wherein R₁ is a phenyl radical or aliphatichydrocarbon radical of the formula C_(n) H_(m) wherein n is an integerof 1 through 8 inclusive and m is equal to 2n+1: R₂ is either hydrogenor a methyl radical; R₃ is a terephthalate or adipate radical: X is 2, 3or 4; and y is 2, 3 or 4. As a general rule, x and y will be equal.Satisfactory results are obtained, however, irrespective of whether xequals y. These ether esters can be produced by the methods disclosed inU.S. Pat. No. 4,620,026, which is incorporated herein by reference. Themost preferred ether esters are di(triethylene glycol butyl ether)terephthalate and di(triethylene glycol butyl ether) adipate. When theseparticular terephthalates and adipates are utilized, they are preferablypresent in the polymer film in an amount within the range of from about5 to about 50 weight percent based upon the total weight of the polymerfilm.

Preferred salt/plasticizer combinations are those in which the salt isCaI₂ or LiI and the plasticizer is a di(triethylene glycol butyl ether)ester of terephthalic or adipic acid.

Suitable as the polymer constituent of the polymer film are poly(vinylchloride), polyurethane, polystyrene, chlorinated polyethylene,poly(vinylidene chloride), poly(ethylene terephthalate), chlorinatedbutyl rubber and isoprene/styrene/butadiene block copolymers. Bothpoly(vinyl chloride) and polyurethane are highly preferred. Polyurethaneis especially preferred as it possesses adhesive qualities which willallow it to make good electrical contact with collector plates or otherconducting surfaces. The polymer films can have a thickness within therange of from about 0.1 to about 10 mils. The thinner polymer films,i.e., those polymer films having a thickness of from about 0.1 to about1 mil, are preferred as these films provide higher discharge voltages.Further, the thinner films allow for the construction of multicellbatteries having a total thickness which is sufficiently small so that aflexible battery is obtained.

As noted previously, the polymer film contains epoxidized vegetable oil.Exemplary of such are epoxidized linseed oil, epoxidized safflower oil,epoxidized soybean oil, epoxidized corn oil, epoxidized cottonseed oiland epoxidized rapeseed oil. Of these, epoxidized soybean oil ispreferred. The epoxidized vegetable oil is generally present in the filmin an amount within the range of from about 2 wt. % to about 10 wt. %based upon the total weight of the polymer film. A preferred amount isabout 5 weight percent.

The polymer film may additionally contain various art-recognizedprocessing aids. For example, solvents, such as, dimethylformamide,tetrahydrofuran, dipropylene glycol and methyl ether acetate, may beused when manufacturing the films of this invention by the solventcasting method. After casting, the solvents should be removed from thefilms to insure good battery performance. When other methods of filmformation are used, other applicable conventional processing aids may beused so long as such do not interfere with the electrolyte function ofthe polymer film.

As taught in U.S. Pat. No. 4,728,588, when using the solidpolyelectrolyte polymer film of this invention to make a secondarybattery, graphite is used to conduct electrical charge to the collectorplates. The graphite is preferably present as a coating on the polymerfilm. If used as a coating, then it is applied by conventionaltechniques, e.g., brushing, spraying, etc.

When the graphite is used as a coating, the coat thickness should bewithin the range of from about 0.1 to about 10 microns. A preferredthickness is from about 1 to about 5 microns. Further, the graphiteshould be very fine, i.e., it should have an average particle sizewithin the range of from about 0.1 microns to about 1.0 microns.

The collector plates act to collect the electrons produced by a batterymade fro films of solid polyelectrolyte polymers during discharge and tofacilitate the application of a recharge voltage to the polymer filmduring recharge. The collector plates may be graphite, carbon cloth orof metal. When carbon cloth is used, a totally non-metal battery orsystem is achieved. When of metal, it is preferred that each collectorplate be of the same metal. By having both collector plates of the samemetal, electrolytic interaction between the plates is avoided. The metalcollector plates are preferably foils of aluminum, copper, brass,platinum, silver or gold.

In a preferred form, the secondary battery made using the solidpolyelectrolyte polymer film of this invention is a laminate of theabove-mentioned polymer film and collector plates. This laminate isconstructed so that the polymer film is captured between the twocollector plates. The resultant laminate can be held togethermechanically or by the use of adhesive. The use of an adhesive requiresthat the adhesive be selected so that its electronic and ionicconductivity does not interfere with the operation of the secondarybattery.

The polymer film of this invention can be prepared conventionally, suchas by drawing, extrusion, by plastisol forming or by the solvent castingmethod. It has been observed that plastisol forming and the solventcasting method give best results. While drawn or extruded films areoperative, their discharge voltage capability is not equal to plastisolformed or solvent cast films. When the plastisol forming method is used,it is important to add the electrolyte to the plasticizer and then toadd the resultant plasticizer/electrolyte salt solution as an ingredientto the rest of the formulated compound. With this manner of addition,higher salt solubilities are obtained and the formation of saltaggregates is avoided.

A feature of the secondary battery prepared from the solidpolyelectrolyte polymer film of this invention is that elevatedtemperatures are not required to achieve useful discharge voltages, butrather that the subject batteries can be conveniently discharged andrecharged at ambient temperatures, e.g., 75° F. (25° C.).

EXAMPLE 1

In a dry box, a 400 ml beaker equipped with a magnetic stirring bar wasplaced on a magnetic stirrer/ heater. To the beaker was added 12 gpoly(vinyl chloride), 6 g of 2-ethyl hexanoic acid tetraethyleneglycol(TEGMER 804), 1 g epoxidized soybean oil, followed by the addition of300 ml of dry N,Ndimethylformamide (DMF). After all of the componentsdissolved in the DMF, 2.5 g of lithium iodide (LiI) was added. Thesolution was stirred and heated for about one hour at 40°-50° C. Thesolution was then divided in half with each half poured into a clearglass plate (25.4 cm×25.4 cm×1.27 cm) which had at least 0.64 cm highsilicone rubber boundaries. The plates were first placed in an ovenwhich had been nitrogen purged. The DMF solvent was allowed to evaporateat an oven temperature between 70° and 80° C. After at least 8 hours,the plates and film were placed in a vacuum oven at 30° C. and fullvacuum for at least 8 hours. The plates were removed and placed in a boxwith a nitrogen atmosphere. Each of the films was cut in half andremoved from the plates. A thin coating of 1 micronsize graphiteparticles was painted on one side of the film and then the other. Thefilm with both sides so coated, was laid on top of a sheet of aluminumfoil having an 18 gauge copper wire connected thereto. On the other sideof the coated film, a like sheet of aluminum foil and wire was thenlaid. An insulating layer of SARAN film was then laid over the lastsheet of aluminum foil to yield a laminate of aluminumsheet/film/aluminum sheet/SARAN film. The resultant laminate was thenrolled, SARAN film to the inside, about a dowel to produce a roll whichin turn was inserted and placed into an appropriate sized poly(vinylchloride) shrink tube. Heat was used to shrink the tube, thus forming atight seal on the laminate with the copper leads exposed, one on eachend of the tube. One lead was attached to the anode of a DC power sourceand the other was attached to the cathode. A charge of ten volts wasapplied for the desired amount of time until the charging currentdecreased to 0.1 mA or less. The charged system was discharged throughan appropriate resistor and the resultant voltage measured. Thedischarge voltage was initially 3.2V at open circuit and 2.1V through a1K ohm resistor. The former discharge voltage was maintained for about 2hours and then slowly decreased to 0.5V over the next 8 hours. When thedischarge voltage became zero, the system was then recharged asdescribed above.

EXAMPLE 2

The procedure in Example 1 was followed except that 2.5 g of CaI₂ weresubstituted for the 2.5 g of LiI used in Example 1. The resultant opencircuit discharge voltage was initially 2.8V which decreased to 0.5Vover 2 hours. The resultant discharge voltage through the 1.0K ohmresistor was 1.5V which decreased to 0.1V over 1/2 hour.

EXAMPLE 3

The procedure in Example 1 was followed except that instead of 6 g, 8 g2-ethylhexanoic acid tetraethylene glycol were used to produce thepolymer film. The resultant open circuit discharge voltage was initially3.0V and maintained over 1 hour. The resultant discharge volume througha 1K ohm resistor was 1.86V and slowly decreased to 0.5V over the next 6hours.

EXAMPLE 4

The procedure in Example 1 was followed except that instead of 2.5 g,3.0 g LiI were used. The resultant open circuit discharge voltage wasmaintained at 3.0V for 1 hour. The discharge voltage through a 1K ohmresistor was initially 2.86V and slowly decreased to 0.5V over an 8-hourperiod.

EXAMPLE 5

The procedure of Example 4 was followed except that instead of 3.0 g,2.0 g LiI were used. The resultant open circuit discharge voltage wasinitially 2.9V. The discharge voltage through a 1K ohm resistor was2.55V and slowly decreased to 0.3V over the next 6 hours.

EXAMPLE 6

The procedure of Example 1 was followed except that conductive carboncloth was used instead of aluminum foil and copper wire as theelectrical contacts. This resulted in a non-metal battery after assemblyand charging. The resultant open circuit discharge voltage was 2.5V. Thedischarge voltage through a 1K ohm resistor was 1.75V which slowlydecreased to 0.5V over 6 hours.

EXAMPLE 7

The procedure of Example 1 was followed except: instead of 12 g, 10 g ofpoly(vinyl chloride) and, instead of 2.5 g LiI, 2.5 g of CaI₂ were used;and the graphite was not used as a coating but instead was provided byadding 0.1 g of 1 micron size graphite to the polymer film producingsolution. The initial open circuit discharge voltage was 1.865V and thedischarge voltage through a 1K ohm resistor was 0.052V and slowlydecreased to zero volts over 10 hours.

EXAMPLE 8

A first electronically conductive polymer film was prepared as follows:

A 25 wt. % lithium iodide solution was prepared by adding lithium iodideto di(triethylene glycol butyl ether) terephthalate.

One hundred parts by weight of dispersion grade poly(vinyl chloride) wasadded to 20 parts by weight epoxidized soybean oil and 33 parts byweight dipropylene glycol methyl ether acetate solvent with mixing.After a substantially homogeneous mix was obtained, 105 parts by weightof 1 micron particle size graphite powder was added thereto with mixing.Then, to this mix was added the di(triethylene glycol butylether)-terephthalate 25 wt. % lithium iodide solution with furthermixing. The resultant mixture was poured onto a smooth glass plate and a"doctor blade" was used to render a film of about 15 mils thickness. Thefilm was cured in an air blown oven for 15 to 20 minutes at about 125°C.

A second electronically conductive film was prepared in the same manneras was the first, except that, instead of lithium chloride, zincchloride was used.

An ionically conductive film was prepared by the following procedure. Adi(triethylene glycol butyl ether) terephthalate 1 wt. % sodiumtetraphenylborate solution was prepared by adding the salt todi(triethylene glycol butyl ether) terephthalate with heating (30° C.)and stirring.

Under mixing, 100 parts by weight of dispersion grade poly(vinylchloride) was added to 20 parts by weight epoxidized soybean oil and 33parts by weight dipropylene glycol methyl ether acetate. A homogeneousmix was obtained. To this resultant mixture, the di(triethylene glycolbutyl ether)terephthalate 1 wt. % sodium tetraphenylborate solution wasadded with mixing. This last mix was poured onto a smooth glass plateand reduced to a thickness of about 15 mil with a "doctor blade". Thefilm was cured in an air blown oven for 15 to 20 minutes at about 125°C.

A laminate was then formed to provide a battery. The laminate consistedof: a first, generally square, 9 in2, brass plate of about 2 milsthickness, a coextensive layer of the first electronically conductivepolymer; a coextensive layer of the ionically conductive polymer; acoextensive layer of the second electronically conductive polymer; and asecond, generally square, 9 in2, brass plate of about 2 mils thickness.The laminae were then mechanically pressed together between two platesof nonconductive material, e.g., plexiglass. An anode lead was connectedto the first brass plate and a cathode lead was connected to the secondbrass plate.

A constant 400 mA, variable voltage DC charging current was applied tothe cathode. The voltage varied from 2 volts to 100 volts and was variedto maintain the constant 400 mA value during charging. The initialcharge period was 8 hours. Subsequent charge periods took only about 5hours. The charge battery was discharged through a 10,000 ohm resistor.The discharge voltage was 1.5 volts, the discharge amperage was 200microamps and the discharge time was 8 hours.

EXAMPLE 9

The same procedure was followed as in Example 8 except that aluminumplates were used instead of brass plates. The resultant charged batterywas discharged through a 10,000 ohm resistor and the discharge voltagewas 1.5 volts and the discharge amperage was 200 microamps. Thedischarge time was 8 hours. Thus, no difference was seen between usingbrass or aluminum plates.

EXAMPLE 10

The procedure of Example 8 was followed except that instead ofdi(triethylene glycol butyl ether) terephthalate 25 wt. % lithium iodidesolution, a di(triethylene glycol butyl ether)terephthalate 25 wt. %copper chloride solution was used.

The battery was discharged through a 10,000 ohm resistor. Dischargevoltage was 1 volt while the discharge amperage was 16 microamps.Discharge time was 4 hours.

EXAMPLE 11

The same procedure that was used in Example 10 was followed except thatthe brass plates were substituted with platinum plates. The dischargevalues through a 10,000 ohm resistor were essentially the same. Thus,there is little difference seen between the use of brass or platinumplates.

EXAMPLE 12

The same procedure that was used in Example 8 was followed except that adi(triethylene glycol butyl ether)terephthalate 25 wt. % calcium iodidesolution was substituted for both the di(triethylene glycol butylether)terephthalate 25 wt.% lithium iodide solution and thedi(triethylene glycol butyl ether)terephthalate 25 wt. % zinc chloridesolution. Discharge through a 10,000 ohm resistor gave a dischargevoltage of 3.5 volts and a discharge amperage of 100 microamps.Discharge time was 10 hours.

EXAMPLE 13

The procedure of Example 12 was followed except that aluminum plateswere used in place of the brass plates. The discharge values through a10,000 ohm resistor were essentially identical as those reported inExample 12.

Another illustrative example of the application of solid polyelectrolytepolymer film product is a static dissipative film. A film according tothis invention can be coated on one side with graphite and folded withthe graphite between the fold. The folded film can then be heat pressedto form a laminate which functions as a static dissipative film. Suchfilms can dissipate a static charge of 5000 volts in 2 seconds or less.

Other applications for the solid polyelectrolyte film of this inventionwill be readily suggested to those skilled in the art and are includedwithin the scope and spirit of this invention. However, it is desiredthat the present invention be limited only by the lawful scope of thefollowing claims.

What is claimed is:
 1. A solid polyelectrolyte polymer film whichfeatures:a) a polymer, b) a plasticizer for said polymer, c) anepoxidized vegetable oil, and d) an electrolyte disassociatinglysolubilized in said plasticizer, said plasticizer and the solubilizedelectrolyte being substantially uniformly distributed within saidpolymer.
 2. The solid polyelectrolyte polymer film wherein saidelectrolyte is selected from the group consisting of a salt having theformula MX_(a) wherein, M is an alkali metal ion, an alkaline earthmetal ion, a zinc ion, a copper ion, a mercury ion or a silver ion, X isa halogen ion or an acetate ion, and a is the oxidation number of M,sodium tetraphenylborate and alkali metal thiocyanates.
 3. The solidpolyelectrolyte polymer film of claim 1 wherein said electrolyte is asalt having the formula MX_(a) and X is iodide.
 4. The solidpolyelectrolyte polymer film of claim 3 wherein M is selected from thegroup consisting of Zn, alkali metals and alkaline earth metals.
 5. Thesolid polyelectrolyte polymer film of claim 3 wherein MX_(a) is CaI₂. 6.The solid polyelectrolyte polymer film of claim 3 wherein MX_(a) is LiI.7. The solid polyelectrolyte polymer film of claim 1 wherein saidplasticizer is an alkyl ether ester of an acid selected from the groupconsisting of benzoic acid, terephthalic acid, phthalic acid, adipicacid and mixtures thereof.
 8. The solid polyelectrolyte polymer film ofclaim 1 wherein said plasticizer is selected from the group consistingof: an alkyl ether ester having the formula, ##STR3## wherein R₁ is aphenyl radical or aliphatic hydrocarbon radical of the formula C_(n)H_(m) wherein n is an integer of 1 through 8 exclusive and m is equal to2n+1, R₂ is either hydrogen or a methyl radical, R₃ is a terephthalateor adipate radical, x is 2, 3 or 4, y is 2, 3 or 4; ad an alkyleneglycol alkanoic diester of the formula. ##STR4## wherein X is a wholeinteger greater than or equal to 2 but less than or equal to 5, n is awhole integer greater than or equal to 4 but less than or equal to 12,and m=2n+1.
 9. The solid polyelectrolyte polymer film of claim 8 whereinsaid plasticizer is di(triethylene glycol butyl ether) terephthalate.10. The solid polyelectrolyte polymer film of claim 9 wherein saidplasticizer is present in an amount within the range of from about 5 toabout 50 weight percent based upon the total weight of said polymerfilm.
 11. The solid polyelectrolyte polymer film of claim 8 wherein saidplasticizer is di(triethylene glycol butyl ether) adipate.
 12. The solidpolyelectrolyte polymer film of claim 11 wherein said plasticizer ispresent in an amount within the range of from about 5 to about 50 weightpercent based upon the total weight of said polymer film.
 13. The solidpolyelectrolyte polymer film of claim 5 wherein said plasticizer isdi(triethylene glycol butyl ether) terephthalate.
 14. The solidpolyelectrolyte polymer film of claim 5 wherein said plasticizer isdi(triethylene glycol butyl ether) adipate.
 15. The solidpolyelectrolyte polymer film of claim 6 wherein said plasticizer isdi(triethylene glycol butyl ether) terephthalate.
 16. The solidpolyelectrolyte polymer film of claim 6 wherein said plasticizer isdi(triethylene glycol butyl ether) adipate.
 17. The solidpolyelectrolyte polymer film of claim 1 wherein said electrolyte issodium tetraphenylborate.
 18. The solid polyelectrolyte polymer film ofclaim 1 wherein said electrolyte is sodium thiocyanate.
 19. The solidpolyelectrolyte polymer film of claim 1 wherein said polymer is selectedfrom the group consisting of poly(vinyl chloride), polyurethane,polystyrene, chlorinated polyethylene, poly(vinylidene chloride),poly(ethylene terephthalate), chlorinated butyl rubber andisoprene/styrene/butadiene block polymers.
 20. The solid polyelectrolytepolymer film of claim 1 wherein said polymer is poly(vinyl chloride).